Tornado and Flash Flooding in North Carolina, September 25 to 28, 2024

Area Forecast Discussion
National Weather Service Blacksburg VA
637 AM EDT Wed Sep 25 2024

.SYNOPSIS...
A slow-moving frontal system will meander along the Ohio River
Valley over the next several days, triggering rounds of showers
and thunderstorm activity through much of the workweek. Helene
is forecast to move northward from the Gulf of Mexico toward
the end of the work week, and may bring more widespread
rainfall to the region.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 130 AM EDT Wednesday...

Key Messages:

1) Heavy rain and thunderstorms to continue through the early
morning hours.

2) A lull in rainfall during the day, but will see an increase
in rain again tonight across the mountains.

Ongoing rain and thunderstorm activity this morning will
continue through daybreak in association with a stalled surface
front extended south from West Virginia into Western Virginia
and then into the North Carolina Piedmont. Favorable upper
divergence remains overhead as an upper low closes off over the
middle Mississippi Valley. High ambient moisture continue to
pool over the area, thus ongoing rain/storms this morning
continue to be very efficient rain producers. Therefore, the
threat for flooding continues this morning.

CAM guidance suggests there will be a lull in rain/storms late
this morning and into the afternoon hours as the stalled front
lifts north again as a warm front. May even have some pockets of
clearing and peeks of sun by the afternoon.

Attention then turns to the mountains tonight from northwest
North Carolina into far southwest Virginia as deep tropical
moisture begins to be drawn north and interacts with a stalled
front across the Tennessee Valley. A nearly unidirectional
southerly flow up to 500mb directly from the tropics will result
in bands of rain developing and repeatedly training from south
to north over the same areas. Heavy rainfall could begin as
early as tonight across the Carolina mountains and extend north
into southwest Virginia. Confidence has increased enough that a
Flood Watch will be introduced for this region.

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
As of 200 AM EDT Wednesday...

Key Messages:

 - Outer rain bands from Tropical Storm Helene will enter the
   area Thursday night.

 - 1 to 5 inches of rain is possible with the highest amount in
   the NW NC mountains.

 - Breezy and Gusty winds are likely Thursday night into Friday.

An upper level low will wobble in the vicinity of Memphis TN
while an upper level ridge sits off the southeast coast. These
two systems will help guide Tropical Storm Helene as it enters
the Gulf of Mexico. Tropical Storm Helene is expected to become
a hurricane as it moves over the warm waters of the eastern Gulf
of Mexico Thursday. Helene is expected to move inland around
the Big Bend area of Florida Thursday evening, then turns
northward towards the southern tip of the Appalachian mountains
(NE GA) Thursday night. Rain showers are forecast to enter the
North Carolina High Country between midnight and sunrise Friday
morning. The rain shield of moderate rainfall could possibly
extend northward into SE WV and the Virginia Highlands during
the morning commute Friday. Helene will then make a turn to the
northwest as it gets caught up in the upper low. Tropical rain
bands will move across RNK's forecast area through late Friday
afternoon. Helene is expected to get absorbed into the upper low
Friday night.

Rainfall amounts will generally range between 1 to 2 inches
across the area. Rainfall amounts of 2 to 5 inches are possible
for counties bordering the Blue Ridge from Roanoke County VA
southward into Watauga County NC.

Winds from Helene will range between 15 to 25 MPH with gusts as
high as 40 MPH late Thursday night into Friday morning. The
higher end of the range will primarily be across the NW North
Carolina High County, the Grayson Highlands and the Mountains
Empire of SW Virginia between midnight and noon Friday. Even
though winds speeds will not reach advisory criteria, shallow
rooted trees could topple as ground will be saturated.

High temperatures Thursday and Friday will range from the mid
60s to mid 70s across the mountains and in the 70s over the
foothills and piedmont. Humidities will remain high with a
tropical airmass over the region.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
As of 230 AM EDT Wednesday...

Key Messages:

1) Tropical airmass remains through Saturday.

2) Cooler weather arrives Sunday behind a cold front.

3) Low rain chances are possible each day through the middle of
next week.

As Tropical Storm Helene begins to dissipate over the
Appalachian mountains early on Saturday, remnant moisture and
breezy conditions will remain across the area. Rain chances
decrease significantly on Saturday but remain possible. High
temperatures will be in the 70s, with eastern piedmont locations
around 80. For Sunday, surface high pressure over New England
will begin to wedge back into the RNK CWA, pushing drier and
cooler air southward. Residual moisture from Helene will
continue to ride over top of this wedge, leading to light
showers and cloudy conditions continuing into early next week.

Due to the cloud cover and high pressure wedge, temperatures
are expected to remain below normal beginning on Sunday. Highs
will be in the 60s and 70s, with lows in the 50s to around 60
degrees through midweek. Winds also remain slightly elevated due
to the wedge. There is some model disagreement with where the
remnant low and associated moisture will go early next week. The
Ensemble Situational Awareness Table continues to keep
precipitable water values around 1.5 inches for early next week.
Due to this, PoPs are kept modest through the forecast period,
with showers possible each day.

&&

.AVIATION /12Z WEDNESDAY THROUGH SUNDAY/...
As of 635 AM EDT Wednesday...

Poor flying conditions with widespread IFR/LIFR across the
area. A combination of low cigs/vsby, along with areas of heavy
downpours may linger a few hours after sunrise. Should see some
slight improvement during the late morning as rain begins to
come to an end. However, sub- vfr cigs are still likely for the
mountains throughout most of the day. A period of low end VFR
for ROA/LYH/DAN possible mid/later afternoon with some modest
clearing possible.

Rain and thunderstorms will increase again tonight along and
west of the Blue Ridge, and especially for the North Carolina
mountains and for southwest Virginia. Outside of the heavy rain,
low cigs/vsby will result in another round of widespread
IFR/LIFR late in the TAF period.

EXTENDED AVIATION OUTLOOK...

MVFR/IFR stratus and fog are expected to occur in rounds through
at least the end of the week, and increasingly likely to
persist through the end of the workweek.

Low pressure lifting northward from the Gulf of Mexico toward
the end of the week may bring more widespread rainfall and sub-
VFR conditions to the region.

&&

.RNK WATCHES/WARNINGS/ADVISORIES...
VA...Flood Watch from 2 PM EDT this afternoon through Thursday
     evening for VAZ007-009-015.
     Flood Watch until 8 AM EDT this morning for VAZ016-017-032>034-
     043>046-058-059.
NC...Flood Watch from 2 PM EDT this afternoon through Thursday
     evening for NCZ001-002-018-019.
     Flood Watch until 8 AM EDT this morning for NCZ003>006-020.
WV...None.

&&

SYNOPSIS...BMG
NEAR TERM...BMG
SHORT TERM...RCS
LONG TERM...JCB
AVIATION...BMG

Hazardous Weather Outlook
National Weather Service Blacksburg VA
258 AM EDT Wed Sep 25 2024

VAZ010>014-018>020-022>024-035-047-WVZ042>044-507-508-260700-
Bland-Giles-Wythe-Pulaski-Montgomery-Craig-Alleghany VA-Bath-Roanoke-
Botetourt-Rockbridge-Amherst-Buckingham-Mercer-Summers-Monroe-
Eastern Greenbrier-Western Greenbrier-
258 AM EDT Wed Sep 25 2024

This Hazardous Weather Outlook is for central Virginia, southwest
Virginia, west central Virginia and southeast West Virginia.

.DAY ONE...Today and tonight.

Heavy rain this morning may result in localized flooding.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

Heavy rain associated with Tropical Cyclone Helene could result in
areas of flooding on Thursday and Friday.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not expected at this time.

NCZ003>006-020-VAZ016-017-032>034-043>046-058-059-260700-
Surry-Stokes-Rockingham-Caswell-Yadkin-Carroll-Floyd-Patrick-
Franklin-Bedford-Henry-Pittsylvania-Campbell-Appomattox-Halifax-
Charlotte-
258 AM EDT Wed Sep 25 2024

...FLOOD WATCH REMAINS IN EFFECT UNTIL 8 AM EDT THIS MORNING...

This Hazardous Weather Outlook is for north central North Carolina,
northwest North Carolina, central Virginia, south central Virginia,
southwest Virginia and west central Virginia.

.DAY ONE...Today and tonight.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Flood Watch.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

Heavy rain associated with Tropical Cyclone Helene could result in
areas of flooding on Thursday and Friday.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be needed.

NCZ001-002-018-019-VAZ007-009-015-260700-
Ashe-Alleghany NC-Watauga-Wilkes-Tazewell-Smyth-Grayson-
258 AM EDT Wed Sep 25 2024

...FLOOD WATCH IN EFFECT FROM 2 PM EDT THIS AFTERNOON THROUGH
THURSDAY EVENING...

This Hazardous Weather Outlook is for northwest North Carolina and
southwest Virginia.

.DAY ONE...Today and tonight.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Flood Watch.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Flood Watch.

Heavy rain associated with Tropical Cyclone Helene could result in
areas of flooding on Thursday and Friday.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be needed.

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